A restrictive clause is not preceded by a comma and it is making a clear distinction about the subject in the sentence.
That is the reason why, the only sentence that includes a restrictive clause is the third one, in order: "The ceramic cups Birgit bought at the garage sale are al chipped."
The answer to your question would be that the sentence that includes a restrictive clause is the following one: The ceramic cups Birgit bought at the garage sale are all chipped.
The sentence above contains a reduced relative clause because it does not contain the relative pronoun (a). What is more, it is restrictive because it adds essential information to the sentence; it helps identify the noun it modifies (the ceramic cups Birgit).
a) The ceramic cups Birgit which were bought at the garage sale are all chipped.
